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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Article
Effects of Sorptive Tendency of Shale on Borehole Stability
Author(s)
Vahid Dokhani1 and Mengjiao Yu2
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DOI:10.17265/2328-2193/2016.05.001
Affiliation(s)
1. YU Technologies, Inc., Tulsa, OK 74133, USA
2. McDougall School of Petroleum Engineering, University of Tulsa, Tulsa, OK 74104, USA
ABSTRACT
Interactions between aqueous drilling fluids and clay minerals have been
identified as an important factor in wellbore instability of shale formations.
Current wellbore stability models consider the interactions between aqueous
drilling fluids and pore fluid but the interactions with shale matrix are neglected. This
study provides a realistic method to incorporate the interaction mechanism into
wellbore stability analysis through laboratory experiment and mathematical
modeling. The adsorption isotherms of two shale rocks, Catoosa Shale and Mancos
Shale are obtained. The adsorption isotherms of the selected shales are
compared with those of other shale types in the literature. This study shows
that the adsorption theory can be used to generalize wellbore stability problem
in order to consider the case of non-ideal drilling fluids. Furthermore, the
adsorption model can be combined with empirical correlations to update the
compressive strength of shale under downhole conditions. Accordingly, a
chemo-poro-elastic wellbore stability simulator is developed to explore the
stability of transversely isotropic shale formations. The coupled transport
equations are solved using an implicit finite difference method. The results of
this study indicate that the range of safe mud weight reduces due to the
moisture adsorption phenomenon.
KEYWORDS
Wellbore stability, shale, sorption isotherm, moisture content, pore pressure, rock failure.
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